The invention relates to a welding torch comprising a main body, a feed device for a welding rod disposed on the main body and joined to a connecting piece, and a contact pipe received in the connecting piece, the contact pipe having a guide bore.
The invention relates to a welding torch of the type described in the generic part of claims 1 and 2.
Welding torches are already known in which the welding rod is fed to the contact pipe by means of a feed device. These welding torches consist of a main body in which a feed device for a welding rod is arranged. The feed device is joined to a connecting piece which receives the contact pipe. In order to provide a better guiding action for the welding rod, the feed device, which may consist of a copper pipe for example, houses a guide device. To this end, the guide device is designed to have an external diameter smaller than the internal diameter of the feed device. Furthermore, the internal diameter of the guide device more or less corresponds to the external diameter of the welding rod so that the welding rod is accurately guided in the guide device. The guide device extends from the hose pack, which is connected to the welding torch, as far as the contact pipe. The disadvantage of a welding torch of this type is that because the welding rod is fed flexibly through a flexible hose pack for the welding rod, it may have a tendency to develop a flex or bend, preventing the welding rod from being introduced automatically into the contact pipe.
The underlying objective of this invention is to provide a welding torch in which the feeding and placing in contact of the welding rod can be improved.
In a welding torch of the first-described structure, this object is accomplished with a contact pipe which has a bore for the welding rod and in which the guide bore has a larger diameter and is concentric with the bore for the welding rod. The welding torch comprises a guide device for the welding rod disposed in the feed device and extending into the guide bore of the contact pipe and from the connecting piece in a direction away from the contact pipe, the guide device being comprised of a flexible, elastically non-conductive material. The advantage of this system is that the welding rod is fed through a matching bore of the contact pipe producing accurate positioning as it leaves the feed device. Another advantage resides in the fact that because the guide device provides an, accurate guiding action across the length of the bore in the contact pipe, the welding rod can be straightened, in particular to remove any bends in the welding rod, so that the welding rod enters the bore of the contact pipe without kinks, which will at least reduce friction of the welding rod in the bore of the contact pipe. Also, the flexible guide device can adapt to bending in the welding rod, thereby ensuring that the welding rod can be easily guided to the contact pipe without current, thereby preventing any sparking or arcuing in the interior of the welding torch or feed device.
According to another aspect of the invention, a welding torch of the first-described structure comprises a bridging piece in the region of the connecting piece and projecting into the guide bore of the contact pipe, and a guide device for the welding rod disposed in the feed device andextending in the guide bore from the connecting piece in a direction away from the contact pipe, the guide device being connected to the bridging piece.
A guide bore having a larger diameter than that of the bore for the welding rod enables the welding rod to be accurately positioned telative to the contact pipe.
If there is a transition region between the bore for the welding rod and the guide bore, which has a conical taper, the welding rod emerges from the guide device, the welding rod is deflected in a direction towards the bore of the contact pipe because of the conical tapered design, enabling the welding rod to be fed along automatically.
Preferably, the bridging piece is composed of several components of different materials, such as a holder component and a guide component. Such a bridging piece is inexpensive to make since only the parts used to guide the welding rod need to be made from a high quality material, which is preferably highly resistant to friction.
A guide component projecting into the guide bore of the contact pipe offers a simple way of positioning the welding rod accurately for the contact pipe.
If the guide component is preferably threadedly connected to the holder component the guide component of the bridging piece can be readily adapted to suit different welding rods.
The bridging piece is prevented from moving if the holder component has a bearing face in a transition region to the guide component.
The advantage of at least a part of the holder component projecting into the feed device is that the radius of the guide device as it emerges from the feed device is not too small, since it would otherwise be impossible to feed the welding rod to the contact pipe automatically.
If the holder component and the guide device are threadedly connected, the guide device is prevented from working loose from the bridging piece due to pulling and pushing movements of the welding rod.
Resistance can be kept low as the wire is fed through a guide device which has an external diameter preferably 10% to 50% smaller than the internal diameter of the feed device, which is a copper pipe, and an internal diameter at least slightly larger than an external diameter of the welding rod.
A reliable contact of the welding rod with the contact pipe, enabling a transfer of current into the contact pipe, is obtained if the contact pipe bore has a diameter that is slightly larger than an external diameter of the welding rod.
When the welding torch is used with a welding robot, it can be duly positioned to reach weld spots that are not readily accessible if the main body has a curved end section.
The welding time for a welding process can be significantly increased if a cooling device consisting of at least two coolant supply lines is disposed in the main body.
Preferably, the feed device is connected to a source of an inert gas, the feed device and the connecting piece having radially aligned bores in a transition region between the connecting piece and an end region of the feed device so that an inert gas atmosphere is produced within the welding torch or contact pipe, preventing corrosion of the welding torch and its individual components.
The welding rod may be made of a soft metallic material so that, by using the bridging piece in conjunction with an aluminum welding rod having a low natural stiffness, the welding rod can be duly positioned or aligned.